Re: [FlyRotary] auto troubleshooting
question
Trying to help a friend get his recently
purchased 2nd
gen running. He has a street ported 13b with a weber
copy side draft carb. The engine starts and runs fine
for about 3 minutes and then it starts
backfiring/popping (a little) and loses power and
quits. Let it sit for a while and it will start back
up and run ok again for another 3 minutes.
I donít think itís the fuel pump cutting out since he
has it hardwired on and it seems to be putting out
plenty of flow.
What else to look for?
Thanks guys!
Joa
It is fuel starvation, first of all
you need 4 psi and at least 14 gph fuel flow and it should run on a
car.
Also the passages in the Weber
between the fuel inlet and the needle and seat are way to small to
flow the fuel we need so you need to pull the top of the carb off and
drill them out larger and leave out the strainer screen under the
brass cap as it is to restrictive.
Also run the biggest needle and seat
they make and warning do not run the after market ones that are called
a gross valve as they tend to stick in the closed
position.
With that it should run in a car but
for the long high power climb outs that aircraft demand you will need
to bump the pressure to 6 psi.
What I do is I have my main pump set
at 4 psi and my auxiliary pump set at 8 psi and on takeoff and climb
out I run both pumps for the safety aspect and to boost the
pressure.
I have found that for the best power
I need to flow 18 gph, 16 will do but there is more power at 18 gph,
if the fuel pressure is 4 psi the flow drops below 14 gph at full
throttle it will starve the float bole.
The best jetting that I have found
for the 48 Weber is 190 main gas, 155 air and f-7 emulsion
tubes.
Ken Welter
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